Supposed to bottle tonight, but the lager started fermenting again when out of fridge

I brewed the Oktoberfest kit from AHBS, let it sit in primary for 12 days at 50 degrees, then transferred to secondary and brought it down to 40 degrees, where it's been for 3.5 weeks (kit recommends 3-4). I hadn't seen any activity from the airlock for about the last 6 days, so 3 days ago I decided today would be bottling day (I have a cousin that comes over and helps so we have to schedule these things).

Just now I brought the carboy upstairs from the basement fridge, and within minutes the airlock was bubbling again. That was an hour ago. It has slowed down since, but is still bubbling at a slow, regular pace. I haven't measured the FG yet.

Would you recommend bottling today anyway, or sticking it back in the fridge?

I bet it's bubbling because the dissolved co2 comes out of solution at warmer temperatures.

If you check the FG, and it's still the same as it was 6 days ago (or the last time you checked), it's fine to bottle.

BONUS ABV !!!! Its probably related to the beer warming up a bit when you brought it up to a warmer room. I've never brewed a Lager, so I don't know if its okay to bottle or not.

YooperBrew said:

I bet it's bubbling because the dissolved co2 comes out of solution at warmer temperatures.

If you check the FG, and it's still the same as it was 6 days ago (or the last time you checked), it's fine to bottle.

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This......

Airlock bubling DOES NOT mean fermentation is necessarily happenning. It means it is offgassing co2...that's not the same thing. Your airlock is a valve to release excess CO2, it is not a fermentation gauge. Your Hydrometer on the other hand IS a fermentation gauge. So until you use that...you don't know that your beer is fermenting again....or that it is releases co2 as the beer warms up.

YooperBrew said:

I bet it's bubbling because the dissolved co2 comes out of solution at warmer temperatures.

If you check the FG, and it's still the same as it was 6 days ago (or the last time you checked), it's fine to bottle.

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+1

When you take your hydrometer sample, make sure to let it warm up to 60F (or whatever your hydrometer is calibrated for) so you get an accurate reading. Draw off your sample and put the rest of the beer back in the cooler with the airlock on. It won't take very long for the sample to come up to temp so keep an eye on it. When you place the hydrometer in the vial, spin the hydrometer to throw off any bubbles that have adhered to it and take your reading at the meniscus. Like Yooper said; when beer warms up, dissolved CO2 comes out of solution and forms bubbles that rise to the surface and burst. This causes the pressure in the headspace to increase which causes the airlock to bubble. Chances are, you are okay to bottle right now but taking a new reading is not a bad idea.